Objective In recent years, due to the rapid development of human society and global warming, the Ordos Relict Gull National Nature Reserve has experienced a yearly shrinkage in water body area, a decline in water level, the loss of the central lake island, and a sharp decrease in the number of relict gulls. As an important intervention to supplement ecosystem water resources, ecological water replenishment plays a vital role in soil and water conservation. This study aims to investigate the impact of ecological water replenishment on the landscape pattern changes in the Ordos Relict Gull National Nature Reserve by comparing changes in water body area, vegetation coverage, landscape type, and spatial distribution before and after replenishment, thereby providing a reference for the protection and restoration of degraded wetlands.

Methods The Ordos Relict Gull National Nature Reserve was taken as the study area. Ten periods of remote sensing images from 2000 to 2022 were selected, covering the periods before (2000–2018) and after (2018–2019) ecological water replenishment. Water bodies were extracted, and land use types were classified using ENVI 5.3 and ArcGIS 10.7. Land type transition matrices were used to analyze the transition trends among land use types. Landscape pattern indices from 2000 to 2022 were calculated using Fragstats 4.2. Based on these analyses, changes in water body area, vegetation coverage, and landscape pattern were evaluated to elucidate the influence of ecological water replenishment.

Results 1) Before ecological water replenishment, the water body area began to shrink from the eastern part of the lake, reaching its minimum value of 1.84 km² in 2012. After ecological water replenishment, the water body boundary expanded 3.41 km towards the eastern bank in the first year, accompanied by an area increase of 4.2 km², and it continued to show a fluctuating increasing trend. 2) Before replenishment, cultivated land and grassland accounted for 28.7% and 34.3% of the reserve, respectively. After replenishment, the proportion of water body area increased from 2% to 5%. The largest patch index and landscape shape index values increased, and the water body became the dominant patch type. 3) The aggregation index and contagion index values showed minimal changes before and after replenishment, indicating relatively stable connectivity. In contrast, Shannon’s diversity index and Shannon’s evenness index values decreased first and then increased, reaching 1.72 and 0.88 in 2022, respectively, indicating an increase in landscape diversity.

Conclusions The implementation of the ecological water replenishment project effectively increases the water body area and improves hydrological conditions within the Ordos Relict Gull National Nature Reserve. This establishes a favorable water foundation for vegetation restoration, leading to significantly improved vegetation coverage and a shift toward a more complicated and diversified landscape pattern. These changes positively contribute to ecosystem stability, result in more sustainable soil and water conservation effects, and provide an improved habitat for rare and endangered bird species. Furthermore, this study expands the application of landscape ecology in evaluating ecological engineering benefits and provides a methodological framework for related research in similar wetland reserves.